This invention relates to a synchronizing mechanism for throttle valves of multiple carburetors and more particularly to an improved synchronizing mechanism that will insure that the throttle valves of the carburetors are in their proper positions with respect to each other.
The induction system for many internal combustion engines, particularly those having multiple combustion chambers, frequently employ a plurality of throttle valves. It is normally the practice for the throttle valves to be interconnected by means of a linkage system so that the throttle valves will all be opened and closed in unison. However, the linkage system between the individual throttle valves frequently employs an arrangment that requires some lost motion in the system so as to insure smooth operation. Where this is the case, it is important to insure that the throttle valves all are in the same position at idle so that they will all be opened at the same time and at the same rates. A variety of synchronizing mechanisms have been previously proposed for this purpose. The systems, however, have certain disadvantages inherent within them, as will now be described.
FIG. 1 illustrates a conventional prior art type of throttle control mechanism wherein the associated internal combustion engine is provided with three throttle valves having throttle valve shafts 11, 12 and 13. The throttle valve shafts 11, 12 and 13 each have affixed to them respective throttle control levers 14, 15 and 16. As is conventional, one of the throttle valves, in this instance that associated with the throttle valve shaft 11, is controlled by a follower mechanism 17 from a cam, in a manner which will be described. The lever 14 carries a pin 18 that is received within an eyelet opening in a linkage mechanism, indicated generally by the reference numeral 19, and which includes a link 21 in which this opening is formed. Corresponding links 22 and 23 are provided with openings that receive pins 24 and 25 that are affixed to the respective levers 15 and 16 so that the throttle valve shaft 11 acts as a main throttle valve and the throttle valve shafts 12 and 13 are opened as slaves.
In order to permit smooth throttle operation, the link eyelet openings have a greater diameter than the diameter of the pins 18, 14 and 25 so as to permit smooth operation. Because of this, when the throttle valve shaft 11 is rotated through an angle .crclbar. in order to effect its opening, the pin 18 will traverse the opening in the link 21 and no movement of the throttle valve shafts 12 and 13 will occur. The throttle valve shaft 12 will not begin to open until the gap x has been closed and the throttle valve shaft 13 will not begin to open until the gap y has been closed.
In order to avoid this problem, a construction is employed wherein the link 15 is split into two link halves 26 and 27 and the link 16 is split into two link halves 28 and 29. The link halves 26 and 28 are affixed to the throttle valve shafts 12 and 13, respectively. The link halves 27 and 29 are journaled on these respective throttle valve shafts and may rotate relative to them. Lock screws 31 and 32 are incorporated so as to insure that the link halves are affixed to each other in the appropriate position to take up the lost motion at idle.
Therefore, as shown in FIG. 2, when the throttle valve shaft 11 is set in its idle position by the idle adjusting screw 33, the respective link halves 26 and 27 and 28 and 29 may be appropriately adjusted so that all of the clearances are taken up in the same direction in the throttle mechanism. However, this is a very complicated and cumbersome arrangement.
FIGS. 3 and 4 show another prior art construction which is designed so as to attempt to simplify this type of construction. As seen in these figures, the linkage system is basically the same. However, in accordance with this type of construction, a torsional spring 41 is employed in each of the split links 15 and 16 so as to bias the link halves 26, 27 and 28, 29 in opposite directions so that when the screws 31 and 32 are locked, the parts will be held in the desired relationship. Although this seems to be feasible at first, the disadvantage is that the rotation of the locking screw 31 and 32 are in the same direction as the direction of pivotal movement of the links 26, 27 and 28, 29 relative to each other. Hence, the tightening of the screws 31 and 32, because of this disadvantage, tends to cause the link halves to rotate relative to each other and disturb the adjustment. Therefore, the use of the springs 41 for taking up the lost motion and facilitating adjustment are not truly effective.
It is, therefore, a principal object of this invention to provide an improved synchronizing mechanism for the throttle valves of a plural throttle valve internal combustion engine.
It is a further object of this invention to provide an improved throttle valve synchronizing mechanism for a multiple throttle valve internal combustion engine.
It is yet another object of this invention to provide a throttle valve synchronizing mechanism including split throttle levers that are locked together by adjusting screws and wherein the locking of the adjusting screw will not tend to effect rotation of either lever half.